1. Field of the Invention
The present invention relates generally to reinforcing paper generally and, more particularly, to a novel method and means for reinforcing paper which allows application of the reinforcing medium at paper converter line speeds and which results in a selectively reinforced paper in which the paper in the reinforced areas is essentially no thicker than the paper in the unreinforced areas. A particular application is in the production of reinforced, punched filler paper.
2. Background Art
Reinforcement of paper may be of two types: reinforcement of the entire paper or reinforcement of selected areas of the paper. The former type of reinforcement employing starch as the reinforcing medium is ancient and today synthetic polymers are being used in place of starch. The latter type of reinforcement is of particular interest where such paper articles as file cards and filler paper are provided with file holes which mate with holding devices such as loose-leaf binders. Such file holes tend to wear with time and eventually the card or paper may even pull away from the holder. Various mechanical means for reinforcing paper are old and include adhering tabs or strips of metal, fabric, polymeric material, or the like around the file holes or in the area in which the file holes are to be formed. Cards and papers incorporating these mechanical means are generally expensive to manufacture.
A particular disadvantage of mechanical reinforcements placed along one edge of the paper is that a stack of such reinforced paper is thicker on one side, thus rendering it difficult or impossible to properly feed a stack to modern high-speed copiers, computer printers, and the like and potentially causing mechanical problems within such devices. Also, such high-speed devices have heating sections which reach temperatures of 400-420 degrees Fahrenheit, which temperatures can partially melt and distort plastic reinforcements and destroy certain adhesives used to attach mechanical reinforcements. Also, some types of mechanical reinforcements make economical recycling of the paper impossible.
Chemical means of selective reinforcement have been attempted. Some involve the selective placement of a surface coating on paper in the areas which have file holes or in which file holes are to be formed. Such coatings add to the thickness of the paper in the reinforced areas and lead to the problems described above. Other chemical means impregnate the paper with polymeric materials which harden the paper and thus make it unsuitable for some applications such as filler paper. Many chemical methods of selective reinforcement cannot be carried out at the line speeds of paper converters. Many employ environmentally objectionable compounds. Some cannot be applied to low-grade, moisture-sensitive papers. Most employ chemicals not compatible with chemicals already used in paper making. There is no known chemical reinforcement process being used commercially to manufacture filler paper having reinforcement in the areas of the file holes.
Accordingly, it is a principal object of the present invention to provide a method and means for reinforcing paper which adds essentially no thickness to the paper in the areas of reinforcement.
Another object of the invention is to provide such a method and means which way be carried out at the line speeds of paper converters.
An additional object of the invention is to provide such a method and means which may be applied to low-grade, moisture-sensitive papers.
A further object of the invention is to provide a reinforcing process which may be carried out at room temperature.
Yet another object of the invention is to provide a reinforcing process which is economical and environmentally satisfactory.
Yet an additional object of the invention is to provide a reinforced punched filler paper which may be fed in stacks to high-speed copiers, computer printers, and the like.
Other objects of the invention, as well as particular features and advantages thereof, will, in part, be apparent and will, in part, be obvious from the following description and the accompanying drawing figures.